Rednecked Cane Borer, Agrilus ruficollis
(F.)
I. Introduction: This buprestid beetle infests wild and cultivated blackberries and raspberries in the eastern states from Canada to the Gulf of Mexico. Adults are about 6-7 mm (1/4 inch) long, with an irridescent coppery pronotum. A related species, Agrilus rubicola Abeille, may occur concurrently. This species is uniform in color, ranging from copper-colored to irridescent green.
On galled plants, there is less live vegetative growth and more dead wood. There is often reduced berry size and number, as well as vegetative growth with increasing number of galls per plant. Affected canes may not produce fruit. Canes weakened by galls are more subject to winter injury.
II. Biology: Adults are present from May to August, or late April to early June, depending on the region. Females lay white spherical eggs on the trunk, and produce a yellow viscous material from the ovipositor which is smoothed over into a covering, before fading to white or grey. Larvae exit the egg directly into the plant, never becoming exposed, and so are impervious to sprays. Young larvae are restricted to the cambium, circling the cane 3-4 times in a close spiral, girdling the primocane, and producing gall-like swellings. As larvae grow, they extend feeding deeper into wood and pith, and staightening the spiral and heading usually toward the distal end of the cane (tunnels may extend 15 cm below to 64 cm above the gall). Larvae reach a length of 12 mm, and have a pair of horn-like projections on the posterior end. The larvae are white and legless, with a flattened head (the family is often called flatheadeded borers). Larvae winter in the cane, and in March create a pupal chamber. The pupa is formed in late April. The pupal period lasts 20-40 days. When the adult leaves the pupal skin, it remains in the tunnel for about 10 days before chewing a D-shaped emergence hole. Adults feed on foliage for several days before beginning oviposition. They are most easily found on the plants on warm sunny days. There is one generation annually.
IV. Control: Chemical control:
After leaf fall or during winter pruning, note galls. If more
than 10% of the primocanes are infested, or if the number of
primocanes expected to be pruned off is exceeded, a spray in
justified. Examine primocanes for adults twice weekly, beginning
at the beginning of bloom. Damage is minimized when malathion is
applied at intervals of 7-12 days from the time the first
beetles appear (early to mid May) until early June (last
emergence). Often two sprays will suffice, just before bloom and
about two weeks later (or the end of bloom, whichever is later).
Spray toward the base of canes, avoiding areas with any residual
blooms.
The following links may be used for chemical
control recommendations:
Pest
Management Guide for Commercial Small Fruit
Pest
Management Guide for Home Fruit
Cultural control: Remove galled canes
in dormant season or early spring. This is most effective if
nearby wild hosts are eliminated, and also more effective in
open settings (wild brambles in nearby woods provide a source of
wild beetles). Summer pruning also may provide a substantial
reduction in rednecked cane borer infestation, since by the time
new shoots appear, they have escaped much of the oviposition
period of rednecked cane borer.
Biological control: This species is
occasionally parasitized by Barichneumon sp. and other
species. Mortality may be quite high, but the normal degree of
successful biological control is unknown.
See our Virginia Tech Department of
Entomology Factsheet
See factsheet from Kentucky.
V. Other information:
